While I agree with being cautious, this isn't true. My wife and I were in Paris when her wallet was stolen out of her purse (or should I say "pinched"?). The thieves then put two charges on my wife's debit card, one for ~$13, and a second for ~$1200 before we got it shut off. I figure they were seeing if the card was usable on the first one and then charged it for a second time. I called the bank about it (from Europe) and they put a freeze on the card. Within a few days they had refunded the money. What I'm saying here is if the debit card is backed by Visa or MC (has the logo at the bottom right hand corner), they are treated just like credit cards as far as the protection goes. If you have any doubt, check with your bank for the terms of use on the card.
Whenever you use your CC or Debit cards, you are at risk for fraud against those cards. The only way to ensure nothing happens to your cards is to never use them. This is like sticking your head in the sand, though. There are some things you can do to help, such as making sure you are on a secure server when doing purchases (look on the URL line and make sure it says "https://" and not just "http://") before you enter any personal information. Also, go with companies which are established. Using a clearing house like Amazon is a lot less risky than going directly to a company which you've never heard of will save you a lot of grief.